This invention relates generally to disposable diapers and more particularly to an improved fastener system for such diapers.
Conventional disposable diapers, in one popular construction, are comprised of a generally rectangular absorbent pad or filler disposed between a fluid-permeable body facing top sheet and a fluid-impermeable plastic film backing sheet. The filler may be comprised of standard commercially available fluff pulp while the top sheet may be comprised of a standard commercially available nonwoven material and the backing sheet may be comprised of a thin sheet of polyethylene. At the lateral side edges of the diaper the backing sheet can be folded around the edges and sealed so that a narrow strip overlies the top sheet while at the ends of the filler the backing sheet and top sheet are bonded together and extend past the top and bottom edges of the filler providing a foldable flap to tuck in against the top sheet upon diapering.
The tape fastener system, in a typical construction, is comprised of a pair of pressure-sensitive tapes that are adhered to the backing sheet at one end of the diaper. Usually the tapes are comprised of two separate parts with one part being the tape having a fixed portion permanently bonded to the backing sheet with the other attachment portion extending, in the closed position, around the side edge to overlie the release liner which is permanently bonded to the top sheet. When ready for use the attachment portion of the tape is removed from the release liner and pulled so as to extend outwardly from the side edge thereby pulling on the plastic backing sheet with the common attachment forces.
A major problem with tapes that are fixed to the plastic backing sheet is that when a person applies tension to the tape, stresses are created within the plastic film that often cause the film to rupture and tear making the diaper unusable. This problem has been recognized and at least two solutions have been proposed. One solution may be seen by referring to U.S. Pat. No. 3,867,940 issued Feb. 25, 1975 to Mesek et al wherein a reinforcing scrim having a higher modulous of elasticity than the plastic film backing sheet is adhered to the thin film in a location at least in the vicinity of where the tape is adhered to the thin film. This construction allows some of the stress to be accepted by the stronger reinforcing material. Another solution may be seen by referring to U.S. Pat. No. 3,900,031 issued Aug. 19, 1975 to Endres et al in which the tape fasteners are attached to the backing sheet in an area where the top sheet is adhered thereto along the entire top edge. In the Endres et al construction the filler material terminates so that it does not extend all the way in the longtudinal direction to the sealed top end margin of the diaper. Each of these tape fastener constructions operates to solve the problem for the particular diaper construction; however, other solutions for various reasons are continually being sought and the present invention is a solution unlike those known in the art.
Accordingly, from the foregoing, one object of the present invention is to provide an improved diaper fastener system that reduces tearing of the plastic film backing sheet.
Another object of the invention is to provide a reinforced structure at the tape attachment area which is economical to manufacture.
Still a further object of the present invention is to reduce tearing of the plastic film backing sheet while still substantially retaining a conventional tape fastener construction.
These and other objects of the invention will become more apparent upon reading the description to follow while referring to the drawings.